Answer:
Mass of aluminium = 21.59 g
Mass of carbon = 124.98 g
Explanation:
Part ii
Given data:
Mass of oxygen = 19 g
Mass of aluminium = ?
Solution:
Chemical equation:
4Al + 3O₂  →   2Al₂O₃
Now we will calculate the moles of oxygen.
Number of moles = mass / molar mass
Number of moles = 19 g/ 32 g/mol
Number of moles = 0.594 mol
Now we will compare the moles of oxygen and aluminium from balanced chemical equation,
     O₂   :    Al
     3    :     4
   0.594  :     4/3×0.594 = 0.8 mol
Mass of aluminium = moles × molar mass
Mass of aluminium = 0.8 mol  × 26.982 g/mol = 21.59 g
Part iii
Given data:
Mass of hydrogen = 42 g
Mass of carbon = ?
Chemical equation:
C  +  2H₂    →  CH₄
Now we will calculate the moles of hydrogen.
Number of moles = mass / molar mass
Number of moles = 42 g/ 2.016 g/mol
Number of moles = 20.83 mol
Now we will compare the moles of hydrogen and carbon from balanced chemical equation,
     H₂  :    C
     2    :     1
   20.83  :     1/2 ×20.83 = 10.415 mol
Mass of carbon = moles × molar mass
Mass of carbon = 10.415 mol ×12 g/mol = 124.98 g
